Based on our in vitro investigation, we have selected 370 nm and 400 nm as suitable excitation wavelengths for clinical studies of oral mucsa. So far we have conducted in vivo studies on 11 volunteers and 13 patients with oral lesions. The studies on volunteers have shown while, the effects of probe pressure, probe angle, and observer techniques on the fluorescence spectral characteristics is not apprecaible, inner patient variabilty is quite high. Thus, in case of lesions, anatomically corresponding contralateral sites were also studied to normlaize inner patient variability. Fluorescence intensity in the blue and red regions were used to devise diagnostic algorithms for differentiating normal from dysplastic sites. The 400-nm excitation wavelength algorithm is better than that for the 370 nm excitation. The preliminary results suggest that the accuracy for detecting dysplastic regions in buccal mucosa is comparable to that of histopathology.